Twisted colon. X-ray of the abdomen of a 68 year old male patient with a twisted sigmoid colon, a condition known as a volvulus. The volvulus has caused the accumulation of gas in the abdomen and it has become distended. The sigmoid colon is the last part of the large intestine before the rectum. Twisting of the intestine can lead to its partial or full obstruction, limiting the intestine's blood supply and the passage of food. Cutting off of the blood supply can lead to tissue death and gangrene, which requiries emergency surgery.